<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>变量对象</title>
</head>
<body>
    <script>
        let  a = 50;
        function f1(){
            console.log("f1的a：",a); // undefined
            let a = 100;
        }
        f1();
        console.log("全局的a：",a); //50
    </script>
</body>
</html>